卫星天线的自动跟踪技术研究

天线自动跟踪技术是卫星移动通信系统的关键技术,其核心问题是天线对卫星的快速捕获和自动跟踪.文中采用了新的步进跟踪算法,进一步提高了系统的跟踪速度和精度.     

基于Simulink仿真的用户星天线控制系统分析

为满足中继卫星系统对天线指向精度的要求,首先描述了天线指向控制概念,对用户星与中继卫星星间链路的建立过程进行了分析,并且设计了星上自主控制方案,在Simulink环境下对所设计的天线指向控制系统进行了数学仿真,最后通过对仿真结果的分析验证了用户星天线控制系统的跟踪性能。     

Performance of a quadricorrelator driven by modulated signals

An analysis is presented of a balanced quadricorrelator driven by a digital-modulated signal with thermal noise. The aim is to assess its performance as a frequency difference detector. The circuit output is decomposed into a signal term and a disturbance referred to as noise. Exprssions are given for the signal and for the power spectral density of the noise as a function of the various system parameters. Design criteria are provided to minimize the output noise for zero frequency offset. In particular, it is found that at high signal-to-noise ratios the noise level can be made vanishingly small by the proper choice of the quadricorrelator filters. A similar result has been recently discovered for another frequency difference detector, the dual-filter detector. It is shown that a balanced quadricorrelator and a dual-filter detector can be made totally equivalent     

测控与雷达天线跟踪方式现状研究及发展趋势

基于航天事业的发展和测控的需求,地面测控网布设的密度越来越大,范围越来越广。为了更好了解和掌握卫星以及航天飞行器在轨运行状况,就需要通过测控天线的精确跟踪来完成。文中对当前测控与雷达天线的几种跟踪方式进行了介绍、分析,并结合未来环境的复杂和多变性,对测控与雷达领域跟踪技术的发展趋势进行了展望。     

卫星扩频信号捕获与跟踪方案分析

信号捕获和跟踪是无线通信中的关键技术.文章针对卫星扩频通信,设计了一种信号捕获及跟踪方案,包括伪噪声(PN)码捕获跟踪和载波捕获跟踪两大部分.从理论上对各模块的性能进行了分析,并利用可编程逻辑阵列(FPGA)验证了该方案的可行性和稳健性.     

一种新型平面阿基米德螺旋天线的分析与设计

对一种新型的平面阿基米德螺旋天线--锯齿状平面阿基米德螺旋天线进行了研究。首先给出了该天线的几何结构,介绍了其主要特点和应用领域,设计并制作了一个2.9~6.2GHz的锯齿状平面阿基米德螺旋天线。测试表明,与普通平面阿基米德螺旋天线相比,该天线能够缩小尺寸,展宽频带,很好地改善天线的低频特性。     

法向模螺旋天线近场耦合的研究

根据天线的近场耦合原理,设计了一种近距离传输数据的双频法向模全向螺旋天线,工作频率在160MHz和480MHz。研究表明,实验数据与天线仿真数据基本吻合。此天线利用近场进行数据传输,不易受外部环境的影响,增加了数据传输的稳定性。     

压制干扰对GPS接收机码跟踪环的性能影响分析

压制干扰是GPS接收机面临的重要的人为威胁之一,对伪码跟踪的跟踪测距精度产生影响,甚至导致伪码跟踪环失锁。干扰对伪码跟踪环的影响模型涉及许多因素,建模比较困难。以常用的非相干超前减滞后功率延迟锁定环为例,建立了码跟踪环在宽带噪声干扰、窄带干扰和点频干扰下的跟踪误差模型,比较了压制干扰对C/A码和P(Y)码跟踪环性能的不同影响。通过对不同干扰方式下C/A码和P(Y)码跟踪误差的仿真,得出了对C/A码和P(Y)码跟踪环性能影响较大的干扰方式和干扰频率,为GPS接收机干扰方法和抗干扰措施的选择提供了理论依据。     

全球地卫天线定位的VB编程实现

针对全球不同区域情况，利用VB语言编制获取天线方位角、仰角的定位程序，它适用于全球地球卫星站天线的定位计算。     

脉冲激励的长方形发射天线的分析与波形优化

在脉冲激励天线中,脉冲波形对于辐射功率有着重要的影响。对长方形行波天线的激励电流脉冲波形与其辐射功率的关系进行了分析。提出了激励电流的优化问题,使得天线在给定方向上的辐射能量最大化。并且给出了优化问题的解法和几种参数下的优化波形。通过具体的数值计算,与其他参考文献中使用的波形相比,优化波形在主辐射方向上可以辐射出更大的能量。     

采用FDTD/FVTD混合算法分析蝶形微带天线

用FDTD和FVTD混合算法分析了蝶形微带天线的反射损失.在适于矩形网格的区域采用常规的非均匀FDTD算法,在微带贴片天线的斜边或PEC弯曲表面处采用FVTD算法,重叠区域的场通过邻近场的线性插值得到.程序仿真和实际测量结果的比较表明在较宽的频带内,该算法在不损失精度,不显著增加CPU时间和内存的情况下,极大地降低了常规FDTD所要求的网格密度.     

一种改进型全向宽带双锥天线的研究

研究了一种用于移动通信的改进型全向宽带天线,采用双锥结构,在馈电处加入短路枝节和寄生套筒,用于调节天线的输入阻抗特性,减小天线尺寸。该天线工作频率为696-2500MHz,高度仅为0．28λmax,直径为6cm,电压驻波比在整个频带内小于1．7,全向特性良好。仿真和实测结果吻合良好,表明该改进型双锥天线在较宽的频带内达到了满意的阻抗特性和方向图特性。     

基于HFSS的多频微带天线分析与设计

设计了一种缝隙多频微带天线。通过在微带天线贴片上加载缝隙改变电流分布,从而实现微带天线的多频谐振。用HFSS软件对其进行仿真分析实现参数的优化设计,在1~6 GHz内得到了3个谐振频率:2.43,4.40和5.27 GHz,其回波损耗分别为:–31.84,–32.82,–29.62 d B。当回波损耗小于–10 d B时,相对带宽分别为:3.29%,1.41%,2.05%。该多频微带天线具有体积小、回波损耗低等优点,可用于无线通讯系统。     

应用摄影测量技术检测大型天线工作状态的研究

在工作状态下对大型天线面型进行高精度测量与调整是当前国内的一个难题,将基于专业数码相机的摄影测量系统应用于大型天线的检测中：采用回光材料制作人工标志,利用编码标志来完成摄站的自动定向和同名点匹配,经光束法平差解算点的坐标,点位的测量精度优于0．11mm,面型的计算精度达到0．4mm,并与全站仪的测量结果进行比较,进一步验证了上述测量结果的正确性。     

Characteristics of an elliptical ring antenna excited by a linear electric probe

This paper presents the characteristics of an elliptical ring antenna excited by a linear electric probe. Based on the waveguide principle, the suitable cross-sectional dimension of the ring that yields the dominant mode (TE_C11 mode) will be formulated in terms of the cut off wavelength. The variation of the antenna characteristics, depending on cross-sectional dimension, ring length and probe length, were investigated using numerical electromagnetic code (NEC) based on the method of moments (MoM). From the experiment, the prototype antenna provides bidirectional pattern with HPBW in E-plane and H-plane of 83 and 46 degrees, respectively, and the gain of 5.1?dBi with SWR?相似文献   

Implementation of a real-time passive ultrasonic angle estimator for autonomous low power ranging and tracking systems

Indoor localisation technologies have received considerable attention in recent years and they are applicable in many fields. As with outdoor systems, they both suffer degradation in performance when multi-path errors are present. Applications include locating essential equipment in hospitals and specific items in warehouses, tracking people with special needs, who are away from visual supervision, and navigating firefighters inside buildings. In this article, we study issues associated with the implementation of a passive low cost, low computational complexity and low power consumption ranging and tracking system using ultrasonic sensor arrays. Due to the physical limitation of these sensors, they are placed in a zig-zag configuration to simulate an approximate linear array. To perform localisation, this system utilises the matrix pencil algorithm to estimate the direction-of-arrival (DOA) of the signal based on the phase delays of the array elements whereas the range estimation is performed by triangulation, based on DOA information from two identical arrays. Multi-access capability is also implemented to accommodate a multiple-transmitter environment. We present real-time experimental results to illustrate the satisfactory performance of the ranging and tracking system in an indoor environment setup.     

利用跟踪控制实现离散线性系统的混沌化

本文利用跟踪控制方法 ,对离散线性系统进行了混沌逆控制研究 ,成功地使非混沌系统混沌化。以二维离散线性系统为例 ,给出了控制器的具体设计方案以及二维离散线性系统的状态与混合光学双稳混沌系统状态之间的误差系统的结构 ,严格地使二维离散线性系统跟踪了混合光学双稳系统混沌的动态行为。这种跟踪控制方法对任意维离散线性系统均适用     

一种自由空间光通信光路的设计与分析

提出了一种用于自由空间光通信的光学系统的设计方法,在这种设计方法中通过卡塞格伦天线实现对激光束的准直,通过偏振分光镜和γ/2波片的巧妙使用来减少杂散光和反射光对信号光的干扰,通过对光学系统的自动跟踪控制消除了通信终端的失准问题。分析和实验表明,基于该光学系统的通信终端激光发散角达到0.4 mrad,对准误差小于6μrad,可实现2 km的自由空间光通信。     

Performance Analysis of a Two‐Hop Fixed‐Gain MIMO Multiuser Relay Network with End‐to‐End Antenna Selection

This letter analyzes the performance of a two‐hop MIMO multiuser relay network with a fixed gain amplify‐and‐forward protocol and antenna selection at the transmitter and receiver. A new expression for the cumulative distribution function of the highest instantaneous end‐to‐end signal‐to‐noise ratio is derived. Based on the above result, closed‐form expressions for outage probability and bit error rate are presented. Also, the diversity order of the system is determined. Finally, computer simulations are compared to the analytical results, and insights and observations are provided.